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Sex Steroid Positive Feedback and the Midcycle Gonadotropin Surge

المؤلف:  Wass, J. A. H., Arlt, W., & Semple, R. K. (Eds.).

المصدر:  Oxford Textbook of Endocrinology and Diabetes

الجزء والصفحة:  3rd edition , p1255

2026-10-21

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 In contrast to the effects of relatively low oestradiol levels, high oestradiol concentrations at midcycle provoke the midcycle gonadotropin surge, characterized by an approximately tenfold increase in LH and an approximately fourfold increase in FSH levels. While some studies suggest that oestradiol alone can produce normal gonadotropin surges, the modest preovulatory increase in circulating progesterone may coordinate the timing of the surge, increase the duration of the surge, and/ or contribute to the midcycle increase in FSH release.

Midcycle levels of sex steroids markedly increase gonadotrope responsiveness to GnRH stimulation. Although midcycle surge generation in women is critically dependent on continued GnRH stimulation and can be prevented with GnRH receptor ant agonists, it remains unclear whether midcycle GnRH surges occur in women. A study involving incomplete GnRH receptor antagonism suggested that GnRH secretion does not increase at midcycle in women. Moreover, pulsatile administration of constant- dose exogenous GnRH— or even reduced dose— produces gonadotropin surges in GnRH- deficient women. Taken together, these findings suggest that sex steroid augmentation of pituitary gonadotropin release is sufficient for gonadotropin surge generation in women.